The 13-year-old son of Chris Keates, general secretary of the National Association of Schoolmasters Union of Women Teachers, was victimised by six pupils.
One pupil has been excluded and two others were taken temporarily out of lessons. The head said: "We have taken the appropriate measures and used the full range of sanctions available to us."
Ms Keates' husband, Les Lawrence, Birmingham city council's cabinet member for education, plans to call a summit of schools in the city to evaluate their anti-bullying policies.
Ms Keates, whose union has a strong stance on bad behaviour, said: "Like all parents we are highly distressed by the circumstances. We want to work with the school to make sure this situation is dealt with and that the problem stops as quickly as possible."
Mr Lawrence admitted that he had felt helpless when he found out: "You go from anger to despair to wanting to provide a more protective framework for your child."
Last week, a woman claimed her daughter killed herself because of bullies.
The mother of Anna Marie Averill, 15, a pupil at Hillcrest School, Birmingham, said the girl was subjected to verbal and physical abuse by three girls over eight months.